Film driving mechanism



April 5, 1938.` A. 1 JEANNE FILM DRIYING MECHANISM Filed Feb. 18, 1937/NVE/vrof? A. L .JEANNE A TTORNE P Patented Apr. 5, 1938 FILM DRIVINGMEOHANISM Armand L. Jeanne, Garden City, N. Y., assigner to BellTelephone Laboratories, Incorporated, New York, N. Y., a corporation ofNew York Application February 18, 1937, Serial No. 126,427

6 Claims.

'Ihis invention relates to film driving mecha'- nisms and moreparticularly to such mechanisms employing a film driven inertia devicefor damping oscillations in the lm.

The object of the invention is to provide anA inexpensive sound filmpropelling mechanism capable of eii'ectively suppressing alloscillations in the driven iilm likely to produce distortion in therecorded or reproduced sound.

A feature of the invention lies in the provision of a iilm driveninertia device comprising two fly-wheels mounted for rotation on asingle fixed stud, one fly-wheel being driven by the film and the othery-wheel being freely rotatable with respect to the first ily-wheel butconnected thereto by a non-positive drivingmeans and a positive drivingmeans contained wholly within the fly.- wheels, the positive drivingmeans being responsive to 4centrifugal force to release the secondy-wheel to the driving action of the nonpositive or slippable drivingmeans alone at running speed. P In a well-known type of sound filmdriving mechanism, a driven film engages and producesv I rotation ofasupporting drum which itself has considerable mass or to which afly-wheel is attached for rotation therewith. yThe mass of the lm drivenily-wheel operates to suppress oscillations transmitted to the film bythe lm so driving means. This type driving means. is not, however,capable of suppressing the resonant oscillations at the naturalfrequency determined by the fly-wheel inertia and the iilm loopstitness..

In an improvedfllm driving mechanism of the type employing a film drivenfly-wheel, the inertia of this low frequency resonant oscillation isdissipated to a great extent by means of a-second fly-wheel freelyrotatable with respect' to' the 40 film driven ily-wheel and driven fromthe film driven fly-wheel through the medium of a viscous iluid. 'I'hecost of this improved iilm driving mechanism employing a viscous liquidas the driving medium is necessarily relatively high and thereforeprojecting apparatus' equipped therewith does not come within a pricerange permitting purchase thereof by a great number of small theaters. H

Applicants invention provides in a film driving mechanism an inexpensivedamping means capable ofeffectively suppressing the resonant oscillationat the natural frequency determined by the ily-wheel inertia and thefilm loop stiffness. 'Ihe damping means of applicant's inventioncomprises a pair of fly-wheels mounted for rotation (c1. Ar11-2.3)

on a common fixed support. One ily-wheel is film driven and the secondy-wheel, which is freely rotatable with respect to the first ywheel, isdriven therefrom at running speed through friction means resilientlymounted on 6 one ily-wheel and engaging the other fly-wheel withsunicient friction to produce rotation of the driven ily-wheel atuniform running speed but permitting relative movement of the drivenflywheel with respect to the driving fly-wheel to 10 dissipate theenergy of the low frequency resonant oscillation at the naturalfrequency determined by the inertia of the fly-wheel and film loopstiffness. A positive driving means responsive to centrifugal force ismounted for operation l5 within the y-wheels to shunt the frictionaldriving means at starting speed.

The invention may be more readily understood by reference to theaccompanying drawing in-w which:

Fig. 1 is a side elevation of a sound picture film projection machinedisclosing the path of a sound picture film from the feed reel to thetake-up reel;

Fig. 2 is an enlarged section taken through the 25 line 2-2 of Fig.' 1disclosing a *film supporting damping means employed at the point ofsound translation;

Fig. 3 is a sectional view of the prism mounting taken though. line 3-3lof Fig. 2; and 30 Fig. 4y is an exploded view in perspective of thepair of fly-wheels disclosed in Fig. -2.

Referring to Fig. 1,.numeral i denotes a picture projection apparatusincluding a fllmgate 2 and a projection lens system included in a tube3.. 35 A film F is drawn from a feedreel located in a reel housing 5 bymeans of a feed sprocket 4. The film is drawn past the pictureprojection aperture lthrough film gate I by means o f an intermittentsprocket 6. `A loop is formed inthe 40 film between intermittentsprocket 6 and a flat film guide 1. After passing the guide l, film Fengages freely rotatable film supporting drum r8 located in housing 9.From the drum tithe film travels to thetake-up sprocket l0 of projectori- 45 and from this sprocket toa take-up reel located in reel -housingIl.

Light from an exciting lamp located in a lamp housing i2 is projected tothe overhanging record portion of the film F on roller 8 by means oflens .50 elements located in an adjustable lens tube i3. An axially.adjustable flanged guide ,roller I4 guides the film to drum 8 andprovides means for adjusting the iilmlaterally in the optical system.

' A right angle prism Ii 5 disposed inwardly of drum .55

8 directs themodulatedl light rays from the fllm 'record to aphotoelectric cell mounted in a door I6 of compartment 9.

Referring to Fig. 2, one end of a stud I1 iits into a boss in the innervertical wall I6 of housing 9 and is held therein by means of a setscrew I9. Stud I1 forms the support for drum 8, fly-wheels and 2|. Aspacing member 22, fitted on stud I1, bears againstanged portion 23thereof. Inner ball races 24, 25 and 26 and spacing members 21, 28 and29 are fitted on stud I1. A nal spacing member 29 tted on stud I1 servesas the anchoring member for a removable prism holder 30. A washer 3| anda spring 32 are clamped against the end of stud I1 by means of a machinescrew 33 which engages a threaded hole 34 (Fig. 4) in the free end ofstud I1. The washer 3| and spring 32 bear against one face of spacingmember 29 under the action of screw 33 to form with the ange 23 aclamping arrangement for the inner ball racesand spacing members; p

Suitable means are provided for mounting prism lI5 in prism holder 30.Prism:- holder 30 slides over spacing member 29. An internal circularflange 36 acts as a stop to limit the inward movement of this prism'holder on the spacing member. A slot 36 provided in member' 29 receivesa pin 31 secured in member 30. As the prism holder is placed inposition, the pin 31 enters slot 38 against the actioniiof spring 32.The slot and pin, therefore, actas means for centering the holder incorrect position. It will be seen that prism holder 30 is readilyremovable from the projecting apparatus for replacement or cleaning.

A single piecev metal member 40 ts into holder Y 30 and is held in placetherein by means of set screws (not shown) located in the prism holder30. As shown in Fig. 3 the member 40 does not extend in front of theprism adjacent aperture 4| ip member 30. Member 40 has a central cutoutportion to receive the prism I5. Top and bottom layers 42 of somesuitable material, such as cork, provide a suitable cushioned mountingfor the prism I5 in member 40. As shown in Figs.

2 and 3, member 40 is provided with a cut-away portion 45 to provideclearance for spring 32.

Outer ball races 50, 5| and' 52 are rotatable on a plurality of ballbearings 53, 54 and 55, respectively. 'I'he drum 8 and its integralily-wheel 20 are fitted on outer ball races 5| and 52 and flywheel 2| istted on outer ball race 50. Internal circular grooves .'iI are providedin th drum 8 to receive split springrlngs 5 1 to pre ent lateralslipping of the drum and fly-wheel 20 relative to the ball bearing. Thesame construction is ap- I plied to fly-wheel 2| to prevent lateralslipping of -surfaces of member 60.

this fly-wheel relative to its b'all bearing.

' Fly-wheel 20 has attached thereto by means of machine screw 59, acircular member 60 having a plurality of stepped coaxial surfaces.Ratchet teeth 6I are formed on one of the stepped coaxial A plurality ofspring members 62 are secured to another stepped coaxial surface ofmember 60 by means of machine screws 63. To the free end of each member62 there is secured a rectangular piece 65 of felt, chamois or othersuitable material which bears against inner surface 66 of ily-wheel 2|under the actionof members 62 to provide a frictional driving connectionfrom y-wheel 20 to fly-'wheel 2 I..

Pins 63 are slidable in slots 69 in ily-wheel 2|.

speed pins 66 engage ratchet teeth 6| on ilywheel 26 to provide apositive drive between the two fly-wheels at starting speed. As theforce of gravity will cause the pin to disengage from the teeththroughout a certain period of rotation of the ily-wheels, a pluralityof spaced pins 66 are provided to insure that at least one pin will bein engagement with the teeth 6| at all times during the starting period.At .running speed centrifugal force causes the pinsv 68 to disengagefrom teeth 6I and thereby release the ily-wheel 2| to the driving actionof the frictional driving members 65. ,Pins 66 are held in slot 69 bymembers 10 which have reduced hooked end portions which act as limitingstops for pins 68. i

The damping means in accordance with this invention will efficientlysuppress low frequency oscillation in the lm. Due to the relativelylarge mass of the ily-wheels and the stiffness of the lm, the naturalfrequency of the damping means as determined by the inertia of theily-wheels and stiffness of the loop of illm engaged in driving`frictionally absorbs the energy of the oscillation.

It is important that the frictional driving means including members 65be set as to pressure to permit slipping when the amplitude of theoscillation is well below a value at which noticeable distortion wouldbe introduced into the recorded or reproduced sound.

By the novel means provided by applicant comprising light spring metalstrips 62, it is possible to resiliently support the felt members 65 incorrect frictional engagement with ily-wheel 2 I. The strips 62 inaddition to providing a resilient support i'or the energy dlssipatingmembers 65 also automatically compensate for wear of these members withuse.

In this disclosure the natural frequency of oscillation of the twofly-wheels is approximately onethird cycle per second. The pressure von'the felt pads is designed4 so that slipping and therefore energydissipation will begin when the instantaneous velocity of the ily-wheelsvaries i-.l per cent from the normal velocity of the fly-wheels.

What is claimed is: l

1. In combination with a lm driving apparatus, a drum arranged to beengaged and driven by the illm, a fly-wheel coupled to said drum, asecond fly-wheel freely rotatable with respect to said drum, meansforming a frictional driving connection between said two fly-wheels, andmeans contained wholly within said fly-wheels forming a positiveconnection between said flywheels at starting speed.

2. In combinationl with a film driving apparatus, a film supportingdrum` adapted to be engaged and driven by the film, vibration dampingmeans associated with said drum, said means comprising a rst fly-wheelcoupledl to said drum. a second ily-wheel of greater inertia than saidrst fly-wheel and freely rotatable with respect to said drum, aplurality of driving means connecting said ily-wheels, one of saiddriving means comprising a plurality of frictional bearing surfacessecured to said rst y-wheeland engaging the surface of said secondfly-wheel to provide a slipping driving connection therebetween, the

other of said driving means comprising va plurality of centrifugallyresponsive devices forming a positive driving connection between saidilywheels at starting speed whereby said first driving means is shuntedduring starting rotation of said drum.

3. A combination in a sound `film recording and reproducing apparatushaving lm driving elements, vibration damping means comprising a pair offly-wheels mounted for rotation on a commonxed stud, one of saidy-wheels adaptedto be driven by said lm and the other of said fly-wheelsbeing freely rotatable with respect to the lm driven ily-wheel, aplurality of driving means mounted on and connecting said ywheels, oneof said driving means being responsive to centrifugal force to releaseits driving connection between said ily-wheels at a predeterminedrotational speed of said freely rotatable ily-Wheel.

4. In combination in a lm driving apparatus, a film supporting drumadapted to be engaged and driven by the lm, vibration damping'meansassociated with said drum, said means comprising a rst fly-wheel coupledto said drum, said first ily-wheel having stepped coaxial surfaces oneof which is provided with teeth, a second flywheel coaxial with Vbutfreely rotatable with respect to said first y-wheel having a centralrecessed area into which several of the stepped coaxial surfaces ofsaidfirst :Ey-wheel project, centrifugally responsive means mounted on saidsecond fly-wheel 'to be engageable with the toothed periphery of one ofthe stepped coaxial surfaces of said first ily-wheel, a plurality ofilexible members each having one end secured to another of the steppedcoaxial surfaces of said first ily-wheel, the free ends of each of saidilexible members frictionally engaging a surface of said secondily-wheel. a

5. In combination in a film driving apparatus,

.a lm supporting drum adapted to be engaged and driven by the film,Avibration damping means associated with said drum, said meanscomprising a first fly-wheel coupled to said drum, a second film drivenfly-wheel, a freely rotatable fiywhee1,

two independently operable driving mechanisms interposed between saidily-wheels, one of said driving mechanisms being responsive to apredetermined rotational speed of said fly-wheels to make itinefl'ective at rotational speeds greater than the predetermined speed.

ARMAND JEANNE.

